Vehicle drive train comprising a retarder and an expander

ABSTRACT

The invention relates to a vehicle drive train, especially for a truck or a rail vehicle, with a hydrodynamic retarder, which has a rotor and a stator or a rotor and a counter-rotating rotor, which together form a working chamber in which a circulating flow of a working medium can be established to hydrodynamically transfer torque from the rotor to the stator or to the counter-rotating rotor, or with a dynamic retarder, which has a rotor and a stator or a rotor and a counter-rotating rotor, in order to transfer torque from the rotor electrodynamically by means of magnetic force, or via liquid or mechanical friction, wherein the transfer of torque or a removal of heat from the retarder is accomplished using a working medium; with an expander that is operated with fluid or steam as the working medium and is used to supply mechanical drive power to the drive train. 
     The invention is characterized in that the retarder and the expander are united with one another by one or more of the following characterizing features:
         the rotor and/or the counter-rotating rotor are drive connected to the expander or such connection can be established;   a heat exchanger is provided, through which the working medium of the retarder and the working medium of the expander are conducted to remove heat from these components and to partially or fully condense the working medium of the expander;   the working medium of the retarder is conducted through a heat exchanger, which simultaneously conducts the working medium of the expander, or through the expander, such that the quantity of heat introduced into the working medium in the retarder is converted to mechanical energy in the expander;   a control system with a pressurized control medium is provided for activating and deactivating the retarder, wherein the working medium of the expander is also the control medium.

The invention relates to a vehicle drive train, especially for a truck, an automobile, a rail vehicle or some other type of vehicle, which has a hydrodynamic retarder for hydrodynamic braking of the vehicle and an expander for powering the vehicle, in other words for providing tractive force, or for powering a component, especially an ancillary component, of the vehicle or the vehicle drive train.

Drive trains that comprise both a hydrodynamic retarder and a steam-powered expander are described in patent specifications U.S. Pat. No. 5,121,607, U.S. Pat. No. 5,241,817 and U.S. Pat. No. 5,195,881. The hydrodynamic retarder is located inside a transmission (CVT), and its rotation is dependent upon the speed of the vehicle. Secondarily, in other words at a secondary output of the transmission, parallel to the transmission output shaft, an expander is provided, which can be used as a compressor for the purpose of braking the vehicle. In compressor mode, rotation of the expander is also dependent upon the speed of the vehicle. The expander can be activated and deactivated in the transmission by means of a cut out clutch.

Although the described vehicle drive trains have both an expander and a hydrodynamic retarder, these two components operate completely independently of one another, so that each requires its own substantial amount of space inside and outside of the transmission, along with its own heat exchanger for removing heat from the two separate working medium circuits and conducting it to the outside. Thus the structural and energy requirements for the proposed vehicle drive train are so intensive that use of this embodiment in practice has not heretofore been feasible.

The object of the present invention is to further improve upon the described vehicle drive train to make it more cost-effective and more energy friendly to produce and to operate, and to increase the output of the vehicle drive train or its operation beyond what is achieved through a simple combination of two known components. The vehicle drive train of the invention should be as structurally compact as possible.

The object of the invention is achieved with a vehicle drive train having the characterizing features of Claim 1. Advantageous and particularly expedient embodiments of the invention are specified in the dependent claims.

The vehicle drive train of the invention has a hydrodynamic retarder. The retarder is either equipped with a stationary, in other words non-rotating, bladed stator and a rotating, bladed rotor, which together form an especially toroidal working chamber, or is configured as a counter-rotating retarder. In the latter case, the retarder has not just one but at least two bladed rotors, referred to here as rotor and counter-rotating rotor, which in retarder mode rotate in opposite directions, that is, in directions of rotation that are opposite one another. The working chamber for the retarder, which is defined by the rotor and the stator or the rotor and the counter-rotating rotor, is either always filled with working medium or alternatively fillable with working medium. If the working chamber is always filled with working medium, the entire retarder can be disengaged from the vehicle drive train, especially from a transmission in the vehicle drive train, by means of a cut out clutch, or other measures for preventing the exertion of retarding torque are provided, such as the free rotation or free dragging of the stator or counter-rotating rotor. If the working chamber of the retarder can alternatively be filled with and emptied of operating medium, it can be activated and deactivated by filling and emptying the working chamber.

In place of the hydrodynamic retarder, or in addition to the hydrodynamic retarder, another dynamic retarder can also be provided, with which torque is transferred from a rotor to a stator or from a rotor to a counter-rotating rotor. Torque can be transferred via liquid friction from a working medium introduced between rotor and stator or between rotor and counter-rotating rotor, for example, or via shear forces in this working medium. Alternatively, or additionally, torque can be transferred via electrodynamic or magnetic force. Finally, torque may be transferred via mechanical friction. Other transfer possibilities are also conceivable. This dynamic retarder can additionally or alternatively have a working medium, or such working medium can flow through said retarder, for the purpose of removing the heat that is created in the retarder.

Also provided in the drive train is an expander, which is operated by a working medium in the form of fluid or steam, in order to generate mechanical operation or drive power via expansion of the working medium. This mechanical power can be supplied to the drive train to provide tractive force to the vehicle, or the expander can be used to power a component, especially an ancillary component, of the drive train or the vehicle, such as a pump, an electric generator, a compressor, or the like.

The expander, also called an expansion engine, can especially be embodied as a piston engine, a screw-type engine or a turbo engine or turbine. In the embodiment comprising a screw-type engine, two screw-type-type rotors engaged with one another are especially provided, which seal off one or more working chambers or expansion chambers via their mutual engagement with one another, and are placed in rotation by the expansion of the working medium in the expansion chamber or chambers.

According to the invention, the hydrodynamic retarder and the expander are not provided simply side by side in a drive train, but are instead integrated with one another. This integration can involve both a mechanical coupling of the two components and a thermal or heat transfer coupling of the two. Alternatively or additionally, it is possible to provide the working medium for the expander, which is then conducted especially in its own working medium circuit which ordinarily comprises a supply pump, as the control medium for the retarder or for a retarder control system. Thus a control air system which is customarily provided for the retarder can be replaced by the supplementary function of the expander or of the working medium circuit of the expander, wherein the expander, in contrast to the customary control air system, is also capable of providing energy-efficient drive power by utilizing heat sources in the vehicle.

According to a first embodiment of the invention, wherein the embodiments described in what follows can also be combined with one another, the rotor and/or the counter-rotating rotor of the retarder and the expander, especially a drive shaft or drive wheel of the same, are in drive connection with one another, or such connection can optionally be established. In this manner, an existing vehicle drive train with a retarder, especially a primary retarder or secondary retarder, can be upgraded especially easily with an expander, with the expander utilizing the same drive connection, especially the same secondary output of a transmission, which was conventionally provided for the retarder. For example, the expander and the retarder can be arranged on a shared shaft with their housings mounted adjacent to one another, or they can be accommodated within a shared housing.

According to a second embodiment of the invention, a heat exchanger is provided for removing heat from the working medium of the retarder, which also acts as a heat exchanger or condenser for removing heat from the working medium of the expander. According to one embodiment, the working medium circuits of retarder and expander are separate from one another, and channels or flow guides for the two working medium circuits, which are correspondingly sealed off from one another, are provided in the shared heat exchanger. According to an alternative embodiment, the working medium of the retarder can also serve as the working medium for the expander.

According to a third embodiment of the invention, the quantity of heat introduced by the retarder into the working medium of the retarder is converted to mechanical energy in the expander. A heat exchanger which transfers heat from the working medium of the retarder to the working medium of the expander can be provided for this purpose. A heat exchanger of this type can naturally also be integrated into the retarder and/or the expander. Alternatively, the working medium can be used as the working medium for both the retarder and the expander. In either case, a storage reservoir can advantageously be provided, which stores the working medium of the expander in its heated or vaporized state, allowing it to be used at a later time, especially once the retarder has been deactivated, to generate mechanical energy in the expander. Especially advantageously, the reservoir is heated and/or thermally insulated so as to minimize or prevent heat loss.

If retarder and expander are coupled mechanically, a speed reduction mechanism is advantageously provided between these two components—based upon the direction of flow of drive power from the expander to the retarder—so that the retarder rotates at a lower speed than the expander. This is especially advantageous if the expander is embodied as a turbine, for example a steam turbine, or as a screw-type expander. Especially favorably, the rotor of the retarder can form or be equipped with external teeth, or can be non-rotatably connected to a corresponding gear with external teeth, especially forming a single piece. The expander, which in this case has a drive shaft with a pinion gear, for example, can then be arranged, especially axially adjacent to the retarder, such that the pinion gear engages with the external teeth or with the externally toothed gear. Drive power from the expander can then advantageously be introduced into the drive train or the transmission via the rotor of the retarder with a freely rotating stator and counter-rotating rotor, or via the drive shaft of the retarder, usually a secondary output in the transmission, when the working chamber of the retarder has been emptied, to supply tractive force to the vehicle. This secondary output can, in turn, be sped up in relation to a transmission output shaft (in the secondary retarder) or a transmission drive shaft (in the primary retarder), so that the retarder rotor also rotates at a higher speed than the transmission drive shaft or the transmission output shaft.

According to one embodiment, the retarder is embodied as a so-called counter-rotating retarder, wherein in retarder braking mode, the counter-rotating rotor is actively powered by the expander, in order to increase the braking torque of the retarder over that of an embodiment having a rotor and a stator. Advantageously, the absolute values of the two speeds of the rotors differ from one another. According to one embodiment, the speed of the counter-rotating rotor can be adjusted so as to regulate or to control braking torque by regulating the power output of the expander, for example by varying the quantity of working medium flowing through the expander.

In what follows, the invention will be described by way of example in reference to several exemplary embodiments.

FIG. 1 shows a first embodiment of the invention with a shared heat exchanger for the working medium of the retarder and the working medium of the expander;

FIG. 2 shows a second embodiment of the invention in which the expander is mechanically coupled to the transmission of a motor vehicle via the rotor of the retarder;

FIG. 3 shows a modification of FIG. 2.

FIG. 1 shows a motor 14 of a vehicle drive train, which is embodied, for example, as a combustion engine, especially as a diesel engine or some other type of piston engine. The motor 14 powers drive wheels 15 of the vehicle via a transmission 10. The transmission 10 can be embodied, for example, as a manual transmission, an automated manual transmission, or an automatic transmission.

On the output side of the transmission 10, in other words opposite the transmission input side, which faces the motor 14 and has a transmission input shaft (not shown) that is driven directly by the motor 14, a retarder 1 is provided in the transmission or—in a variation on this diagram—on the outside of the transmission, which provides hydrodynamic braking of the vehicle. To this end, the rotor (not shown) of the retarder 1 is drive connected to the transmission output shaft 11, which is in turn drive connected to the drive wheels 15.

During the operating mode in which the retarder 1 is activated, in other words during the hydrodynamic braking of the vehicle, heat is generated in the working chamber of the retarder and must be removed via an external cooling circuit 16, usually the vehicle cooling circuit. For this purpose, a heat exchanger 7 is connected to the retarder 1, which conducts the cooling medium for the vehicle cooling circuit and the working medium of the retarder in such a way as to transfer heat from the working medium of the retarder to the cooling medium of the cooling circuit. In this case, the working medium of the retarder can be oil, water, or a water mixture, for example.

In addition to the cooling medium of the cooling circuit and the working medium of the retarder 1, the heat exchanger 7 also conducts the working medium of a working medium circuit 17 of an expander 6. The working medium of the expander 6 is then partially or fully condensed in the heat exchanger 7. Other components of the working medium circuit 17 of the expander 6 include a reservoir 18 for the working medium, a water feed pump 19 and a condenser 20.

As an alternative to the illustrated embodiment, the heat exchanger 7 could also be incorporated into the working medium circuit 17 of the expander 6 so as to allow heat to be transferred from the working medium of the retarder 1 and/or from the cooling medium of the cooling circuit to the working medium of the expander 6. As a rule, the heat exchanger 7 would then be incorporated downstream of the infeed pump 19 and upstream of the steam generator 20 in the direction of flow of the working medium circuit 17 of the expander 6.

Because the working medium of the working medium circuit 17 of the expander 6 has a certain pressure level at least downstream of the water infeed pump 19, for example 6-10 bar, the working medium of the expander 6 could alternatively or additionally act as the control medium for the retarder 1. To enable this, suitable control valves would have to be provided in the working medium circuit 17, to in turn allow control valves of the retarder 1 or in the working medium circuit of the retarder 1 to be activated or controlled or regulated.

The expander 6 shown in FIG. 1 can be used either to drive the vehicle itself, in other words to supply tractive force to the vehicle, or to power a component, especially an ancillary component (not shown) of the vehicle. Alternatively or additionally it is possible, as initially mentioned, for a counter-rotating rotor (not shown) of the retarder 1 to be powered by the expander 6.

FIG. 2 shows a possible mechanical coupling of the expander 6 to a transmission output shaft 11 of a transmission 10 via the rotor 2 of a retarder 1. FIG. 3 schematically illustrates the option of hydrodynamically coupling the expander 6 to the transmission 10 or the transmission output shaft 11 via a retarder 1, which can also be operated as a hydrodynamic clutch. This embodiment offers the advantage that, because of the torsional vibration damping effect of the hydrodynamic clutch, torsional vibrations, which can occur in the transmission 10, are not transferred to the expander 6, which can then especially be embodied as a turbine and can rotate at a very high speed, for example up to 20,000 rpm or more. It is also possible for the expander 6 to power the counter-rotating rotor 4 of the retarder 1 in the opposite direction from the rotor 2, in order to increase the hydrodynamic braking effect of the retarder.

In contrast, in the former embodiment illustrated in FIG. 2 the retarder 1 has a stator 3, which is held alternatively or permanently stationary, in other words not rotating.

In both embodiments represented in FIGS. 2 and 3, a toroidal working chamber 5 is formed in the retarder 2 by the two blade wheels—rotor 2 and stator 3 or rotor 2 and counter-rotating rotor 4—and is optionally tillable with a working medium. If desired, the braking torque of the hydrodynamic retarder 1 can be regulated by means of a fill level control mechanism. According to the embodiment comprising a counter-rotating retarder (FIG. 3), however, braking torque can also be controlled by adjusting the speed of the expander 6.

In both embodiments illustrated in FIGS. 2 and 3, the expander 6 has a drive shaft 8, which supports a pinion gear 9. The pinion gear 9 engages with external teeth 21 either on the rotor 2 or on the counter-rotating rotor 4 of the retarder 1. The rotor 2 of the retarder 1 is powered via a secondary output 12, in other words a power output parallel to the primary output and formed by the transmission output shaft 11, and is primarily non-rotatably held directly on the secondary output shaft 13. The secondary output shaft 13 is drive connected to the transmission output shaft 11 via a pinion gear 22. In this case, the pinion gear 22 on the secondary output shaft 13 engages with a toothed gear 23 on the transmission output shaft 11.

In the illustrated embodiments, the rotor 2 of the retarder is sped up in relation to the transmission output shaft 11 and is slowed in relation to the expander 6 or the drive shaft 8 of the expander 6.

Of course, it is possible to combine the exemplary embodiments of FIGS. 2 and 3 with an embodiment of FIG. 1, or to select individual characterizing features from the illustrated exemplary embodiments so as to arrive at an embodiment according to the invention.

LIST OF REFERENCE SYMBOLS

-   1 Retarder -   2 Rotor -   3 Stator -   4 Counter-rotating rotor -   5 Working chamber -   6 Expander -   7 Heat exchanger -   8 Drive shaft -   9 Pinion gear -   10 Transmission -   11 Transmission output shaft -   12 Secondary output -   13 Secondary output shaft -   14 Motor -   15 Drive wheels -   16 Cooling medium circuit -   17 Working medium circuit of the expander -   18 Reservoir -   19 Water infeed pump -   20 Steam generator -   21 External teeth -   22 Pinion gear -   23 Toothed gear 

1. A vehicle drive train, especially for a truck or a rail vehicle, with a hydrodynamic retarder, which has a rotor and a stator or a rotor and a counter-rotating rotor, which together form a working chamber in which a circulating flow of a working medium can be established to hydrodynamically transfer torque from the rotor to the stator or to the counter-rotating rotor, or with a dynamic retarder, which has a rotor and a stator or a rotor and a counter-rotating rotor, in order to transfer torque from the rotor electrodynamically by means of magnetic force, or via liquid or mechanical friction, wherein the transfer of torque or a removal of heat from the retarder is accomplished using a working medium; with an expander which is operated with fluid or steam as the working medium and is used to supply mechanical drive power to the drive train; characterized in that the retarder and the expander are united with one another by one or more of the following characterizing features: the rotor and/or the counter-rotating rotor are drive connected to the expander or such connection can be established; a heat exchanger is provided, through which the working medium of the retarder and the working medium of the expander are conducted to remove heat from these components and to partially or fully condense the working medium of the expander; the working medium of the retarder is conducted through a heat exchanger, which simultaneously conducts the working medium of the expander, or through the expander, such that the quantity of heat introduced into the working medium in the retarder is converted to mechanical energy in the expander; a control system with a pressurized control medium is provided for activating and deactivating the retarder, wherein the working medium of the expander is also the control medium.
 2. The vehicle drive train of claim 1, characterized in that the expander is mechanically drive connected with the rotor of the retarder, or such a connection can be established, and in that a speed reduction mechanism is provided in the drive connection, so that a drive shaft and/or a rotor of the expander rotates at a higher speed than the rotor of the retarder.
 3. The vehicle drive train of claim 2, characterized in that the rotor of the retarder has external teeth or is non-rotatably connected to a toothed gear, especially forming a single piece, and the expander has a drive shaft with a pinion gear, which engages with the external teeth or with the toothed gear.
 4. The vehicle drive train of claim 1, characterized in that a transmission, especially a manual transmission, automated manual transmission or automatic transmission, with a transmission input shaft and/or with a transmission output shaft, is provided and is used to power drive wheels of the vehicle, and in that the transmission has a secondary output which is sped up in relation to the transmission input shaft and/or the transmission output shaft and which drives the rotor of the retarder, wherein the secondary output especially has a secondary output shaft, which non-rotatably supports the rotor of the retarder.
 5. The vehicle drive train of claim 1, characterized in that the expander is embodied as a turbine, a screw-type engine or a piston engine.
 6. The vehicle drive train of claim 1, characterized in that the rotor of the retarder and the expander, especially a blade wheel or turbine wheel of the latter, are supported on a shared shaft, especially non-rotatably supported.
 7. The vehicle drive train of claim 1, characterized in that the retarder has a rotor and a counter-rotating rotor which rotate counter to one another, and, in an operating mode in which the retarder is activated, the rotor is powered at least indirectly via wheels of the vehicle and especially via the transmission output shaft, and the counter-rotating rotor is powered especially with its speed being regulated by the expander.
 8. The vehicle drive train of claim 1, characterized in that the retarder and the expander are encased within a shared housing.
 9. The vehicle drive train of claim 1, characterized in that the working medium of the retarder is also the working medium of the expander.
 10. The vehicle drive train of claim 1, characterized in that the retarder and the expander each have their own working medium circuit, wherein the working medium circuits are separate from one another in terms of the conductance of working medium, but are connected to one another in terms of heat transfer.
 11. The vehicle drive train of claim 9, characterized in that an especially heated and/or heat-insulated reservoir for storing heated and especially vaporized working medium is provided in the working medium circuit of the expander.
 12. The vehicle drive train of claim 10, characterized in that an especially heated and/or heat-insulated reservoir for storing heated and especially vaporized working medium is provided in the working medium circuit of the expander.
 13. The vehicle drive train of claim 2, characterized in that a transmission, especially a manual transmission, automated manual transmission or automatic transmission, with a transmission input shaft and/or with a transmission output shaft, is provided and is used to power drive wheels of the vehicle, and in that the transmission has a secondary output which is sped up in relation to the transmission input shaft and/or the transmission output shaft and which drives the rotor of the retarder, wherein the secondary output especially has a secondary output shaft, which non-rotatably supports the rotor of the retarder.
 14. The vehicle drive train of claim 3, characterized in that a transmission, especially a manual transmission, automated manual transmission or automatic transmission, with a transmission input shaft and/or with a transmission output shaft, is provided and is used to power drive wheels of the vehicle, and in that the transmission has a secondary output which is sped up in relation to the transmission input shaft and/or the transmission output shaft and which drives the rotor of the retarder, wherein the secondary output especially has a secondary output shaft, which non-rotatably supports the rotor of the retarder.
 15. The vehicle drive train of claim 2, characterized in that the expander is embodied as a turbine, a screw-type engine or a piston engine.
 16. The vehicle drive train of claim 3, characterized in that the expander is embodied as a turbine, a screw-type engine or a piston engine.
 17. The vehicle drive train of claim 4, characterized in that the expander is embodied as a turbine, a screw-type engine or a piston engine.
 18. The vehicle drive train of claim 4, characterized in that the rotor of the retarder and the expander, especially a blade wheel or turbine wheel of the latter, are supported on a shared shaft, especially non-rotatably supported.
 19. The vehicle drive train of claim 5, characterized in that the rotor of the retarder and the expander, especially a blade wheel or turbine wheel of the latter, are supported on a shared shaft, especially non-rotatably supported.
 20. The vehicle drive train of claim 4, characterized in that the retarder has a rotor and a counter-rotating rotor which rotate counter to one another, and, in an operating mode in which the retarder is activated, the rotor is powered at least indirectly via wheels of the vehicle and especially via the transmission output shaft, and the counter-rotating rotor is powered especially with its speed being regulated by the expander. 